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Concern grows over toxic threats to Australia's seas

Dead Whales and dolphins that washed up on Australia’s east coast between
1987 and early 1991 had ‘significant’ levels of organochlorines and heavy
metals in their tissues, according to the researcher who analysed their
remains.

This is the first report of toxic wastes in cetaceans in the southern
hemisphere. It supports growing concerns about the general health of Australia’s
eastern marine environment.

The findings, which were revealed last month at a scientific conference
in Sydney, suggest that pollution has contaminated the food chain in the
region from top to bottom. This conclusion is based on the fact that the
dead animals were odontocetes, or toothed whales and dolphins. These top-level
predators could only have picked up their ‘heavy toxic load’ from the smaller
creatures they eat, said the investigating scientist, Cor Lenghaus of the
Regional Veterinary Laboratory in Hamilton, Victoria.

In turn, the cetaceans’ food species would have acquired the toxins
from shellfish and small bottom-dwelling animals that accumu late pollutants.

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Three of the four whales Lenghaus studied carried a variety of heavy
metals in their bodies, namely arsenic, cadmium, mercury, copper, lead and
zinc. The concentrations varied, but Lenghaus said that all the animals
contained levels of one or more of the metals that were above the levels
at which serious health problems can be expected.

Zinc levels, for instance, ranged from 2.28 parts per million (ppm)
to 26 ppm; acute disease could occur at about 10 ppm, he estimates.

Lenghaus has performed autopsies on a total of nine cetaceans; all had
organochlorines in their blubber. The highest levels were for DDT and its
derivatives.

One adult bottlenose dolphin, for example, showed 37 ppm of DDT, which
is acutely toxic to cetaceans at roughly 10 to 50 ppm. Other, more poisonous
organochlorines present included dieldrin and hexachlorobenzene.

Seven of the animals were sick at the time of their death. ‘Several
young, adult animals had died of severe, generalised bacterial or fungal
infections. This could be a result of immunosuppression caused by the toxins,’
Lenghaus said.

Of the others, one dolphin probably died of old age, and two whales
were stillborn calves. As the babies had never suckled, it is likely that
they acquired the heavy metals and organochlorines from their mothers. Lenghaus
speculates that the toxic levels in the dams must have been ‘horrendous’.

The cetaceans studied had been washed ashore in the state of Victoria.
Although the number of animals Lenghaus examined is small, his results follow
other studies which have already demonstrated marine con tamination along
the coastline, especially in Melbourne’s Port Phillip Bay.

For example, scientists concluded in a technical report written for
the state Marine Sciences Laboratory in 1986 that a large fish kill in the
bay in 1984 was most likely the result of exposure to polycyclic aromatic
hydrocarbons, lead and cadmium.

Extremely high levels of tributyl tin (TBT) in Port Phillip Bay were
also discovered last year by government biologists. The highly toxic compound
is painted on boat hulls to prevent fouling by algae. According to an internal
memorandum in the Department of Conservation and Environment, the level
of 3.5 ppm is the highest reading for sea water ever observed by Robert
Huggett of the Virginia Institute of Marine Science in the US, a leading
expert in TBT.

Officials with the Victoria Environmental Protection Association and
other government agencies claim that these and other pollution problems
are now under control. The use of organochlorines in agriculture and TBT
on boats under 25 metres, for instance, were both banned in 1989.

There is continued scientific concern, nonetheless, because TBT still
enters waters in Victoria from sewage outflows, boat repair yards, and the
hulls of large vessels.